Processing olefin copolymers

ABSTRACT

The invention is directed to essentially saturated hydrocarbon polymer composition comprising essentially saturated hydrocarbon polymers having A) a backbone chain, B) a plurality of essentially hydrocarbyl sidechains connected to A), said sidechains each having a number-average molecular weight of from 2500 Daltons to 125,000 Daltons and a MWD by SEC of 1.0-3.5; and having A) a Newtonian limiting viscosity (η 0 ) at 190° C. at least 50% greater than that of a linear olefinic polymer of the same chemical composition and weight average molecular weight, preferably at least twice as great as that of said linear polymer, B) a ratio of the rubbery plateau modulus at 190° C. to that of a linear polymer of the same chemical composition less than 0.5, preferably &lt;0.3, C) a ratio of the Newtonian limiting viscosity (η 0 ) to the absolute value of the complex viscosity in oscillatory shear (η*)at 100 rad/sec at 190° C. of at least 5, and D) a ratio of the extensional viscosity measured at a strain rate of 1 sec −1 , 190° C., and time=3 sec (i.e., a strain of 3) to that predicted by linear viscoelasticity at the same temperature and time of 2 or greater. Ethylene-butene prepared by anionic polymerization and hydrogenation illustrate and ethylene-hexene copolymers prepared by coordination polymerization illustrate the invention. The invention polymers exhibit improved processing characteristics in that the shear thinning behavior closely approaches that of ideal polymers and exhibit improved strain thickening.

This application claims benefit of provisional application Ser. No.60/037,449 filed Feb. 16, 1997.

TECHNICAL FIELD

The invention relates to improved processing olefin copolymers having aplurality of substantially linear branches and to compositionscomprising them.

BACKGROUND OF THE INVENTION

Ethylene copolymers are a well-known class of olefin copolymers fromwhich various plastic products are now produced. Such products includefilms, fibers, and such thermomolded articles as containers andcoatings. The polymers used to prepare these articles are prepared fromethylene, optionally with one or more additional copolymerizablemonomers. Low density polyethylene (“LDPE”) as produced by free radicalpolymerization consists of highly branched polymers where the branchesoccur randomly throughout the polymer, that is on any number of formedsegments or branches. The structure exhibited easy processing, that ispolymers with it could be melt processed in high volumes at low energyinput. Machinery for conducting this melt processing, for exampleextruders and film dies of various configurations, was designed intoproduct finishing manufacturing processes with optimal design featuresbased on the processing characteristics of the LDPE.

However, with the advent of effective coordination catalysis of ethylenecopolymers, the degree of branching was significantly decreased, bothfor the now traditional Ziegler-Natta ethylene copolymers and those fromthe newer metallocene catalyzed ethylene copolymers. Both, particularlythe metallocene copolymers, are essentially linear polymers, which aremore difficult to melt process when the molecular weight distribution(MWD=M_(w)/M_(n), where M_(w) is weight-average molecular weight andM_(n) is number-average molecular weight) is narrower than about 3.5.Thus broad MWD copolymers are more easily processed but can lackdesirable solid state attributes otherwise available from themetallocene copolymers. Thus it has become desirable to developeffective and efficient methods of improving the melt processing ofolefin copolymers while retaining desirable melt properties and end usecharacteristics.

The introduction of long chain branches into substantially linear olefincopolymers has been observed to improve processing characteristics ofthe polymers. Such has been done using metallocene polymers wheresignificant numbers of olefinically unsaturated chain ends are producedduring the polymerization reaction. See, e.g., U.S. Pat. No. 5,324,800.The olefinically unsaturated polymer chains can become “macromonomers”or “macromers” and, apparently, can be re-inserted with othercopolymerizable monomers to form the branched copolymers. Internationalpublication WO 94/07930 addresses advantages of including long chainbranches in polyethylene from incorporating vinyl-terminated macromersinto polyethylene chains where the macromers have critical molecularweights greater than 3,800, or, in other words contain 250 or morecarbon atoms. Conditions said to favor the formation of vinyl terminatedpolymers are high temperatures, no comonomer, no transfer agents, and anon-solution process or a dispersion using an alkane diluent. Increaseof temperature during polymerization is also said to yield β-hydrideeliminated product, for example while adding ethylene so as to form anethylene “end cap”. This document goes on to describe a large class ofboth monocyclopentadienyl and biscyclopentadienyl metallocenes assuitable in accordance with the invention when activated by eitheralumoxanes or ionizing compounds providing stabilizing, noncoordinatinganions.

U.S. Pat. Nos. 5,272,236 and 5,278,272 describe “substantially linear”ethylene polymers which are said to have up to about 3 long chainbranches per 1000 carbon atoms. These polymers are described as beingprepared with certain monocyclopentadienyl transition metal olefinpolymerization catalysts, such as those described in U.S. Pat. No.5,026,798. The copolymer is said to be useful for a variety offabricated articles and as a component in blends with other polymers.EP-A-0 659 773 A1 describes a gas phase process using metallocenecatalysts said to be suitable for producing polyethylene with up to 3long chain branches per 1000 carbon atoms in the main chain, thebranches having greater than 18 carbon atoms.

Reduced melt viscosity polymers are addressed in U.S. Pat. Nos.5,206,303 and 5,294,678. “Brush” polymer architecture is described wherethe branched copolymers have side chains that are of molecular weightsthat inhibit entanglement of the backbone chain. These branchweight-average molecular weights are described to be from 0.02-2.0 M ,where M_(e) ^(B) is the entanglement molecular weight of the sidebranches. Though the polymers illustrated are isobutylene-styrenecopolymers, calculated entanglement molecular weights for ethylenepolymers and ethylene-propylene copolymers of 1,250 and 1,660 areprovided. Comb-like polymers of ethylene and longer alpha-olefins,having from 10 to 100 carbon atoms, are described in U.S. Pat. No.5,475,075. The polymers are prepared by copolymerizing ethylene and thelonger alpha-olefins which form the side branches. Improvements inend-use properties, such as for films and adhesive compositions aretaught.

DISCLOSURE OF INVENTION

The invention is directed to a polymer composition comprisingessentially saturated hydrocarbon polymers having: A) a backbone chain;B) a plurality of essentially hydrocarbon sidechains connected to A),said sidechains each having a number-average molecular weight of from2,500 Daltons to 125,000 Daltons and an MWD by SEC of 1.0-3.5; and, C) amass ratio of sidechains molecular mass to backbone molecular mass offrom 0.01:1 to 100:1. These invention compositions comprise essentiallysaturated hydrocarbon polymers having: A) a Newtonian limiting viscosity(η₀) at 190° C. at least 50% greater than that of a linear olefinicpolymer of the same chemical composition and weight average molecularweight, preferably at least twice as great as that of said linearpolymer, B) a ratio of the rubbery plateau modulus at 190° C. to that ofa linear polymer of the same chemical composition less than 0.5,preferably <0.3, C) a ratio of the Newtonian limiting viscosity (η₀) tothe absolute value of the complex viscosity in oscillatory shear (η*) at100 rad/sec at 190° C. of at least 5, and D) a ratio of the extensionalviscosity measured at a strain rate of 1 sec⁻¹, 190° C., and time=3 sec(i.e., a strain of 3) to that predicted by linear viscoelasticity at thesame temperature and time of 2 or greater. The invention polymersexhibit highly improved processing properties, improved shear thinningproperties and melt strength.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1-4 illustrate viscometric data of an ethylene-butene copolymer ofthe invention in comparison with similarly obtained data for traditionallow density polyethylene (LDPE) and metallocene low densitypolyethylenes (LLDPE).

FIG. 1 illustrates the complex viscosity vs. the frequency ofoscillatory deformation at 190° C.

FIG. 2 illustrates the normalized viscosity vs. the frequency times thezero shear viscosity at 190° C.

FIG. 3 illustrates the storage modulus vs. the frequency at 190° C.

FIG. 4 illustrates the storage modulus vs. the frequency times the zeroshear viscosity at 190° C.

FIG. 5 illustrates the relation between the extensional viscosity(η_(ext) (linear)) and that measured (η_(ext) (meas)) for a polymer thatshows significant strain hardening.

DETAILED DESCRIPTION OF THE INVENTION

The branched hydrocarbon copolymers according to the invention can bedescribed as those having a main, or backbone chain, of ethylene andother insertion copolymerizable monomers, containing randomlydistributed side chains of ethylene and other insertion copolymerizablemonomers. The backbone chain has a number-average molecular weight fromabout 5,000 to about 1,000,000 Daltons, preferably from about 10,000 toabout 500,000 Daltons, most preferably from about 20,000 to about200,000 Daltons. The side chains have number-average molecular weightsfrom about 2,500 to about 125,000 Daltons, preferably from about 3,000to about 80,000 Daltons, most preferably from about 4,000 to about60,000 Daltons. As expressed in M_(e) ^(B), side chains havenumber-average molecular weights ranging from above 2 to 100 times theentanglement weight of copolymer, preferably 3-70 times the entanglementweight of copolymer, and most preferably 4-50 times the entanglementweight of copolymer. The number of side chains per backbone chain isdetermined by the average spacing between the branches, the backbonesegment between each branch averaging a number-average of at least twicethe entanglement molecular weight of polyethylene, preferably 3 to 25times the entanglement molecular weight of polyethylene. In practicethis establishes a number of arms of from 2-100, preferably 2-70, mostpreferably 3-50.

The MWD, defined as the ratio of number-average molecular weight tonumber-average molecular weight, for both the backbone chain and thesidechains, independently, can be from 1.0-6, preferably 1-5, and mostpreferably 1-3.5. The mass ratio of backbone to sidechain can be 0.1:1to 10:1, 0.3:1 to 3:1, or 0.5:1 to 2:1.

Rheological Properties

Definition of linear viscoelastic behavior of polymeric materials iscomplex, but utilizes well known concepts. Thus, the invention may bedescribed in terms of melt rheological parameters including theNewtonian limiting viscosity, the rubbery plateau modulus, and in termsof “shear thinning” characteristics readily quantified in terms of theratio of the Newtonian limiting viscosity (η₀) to the absolute value ofthe complex viscosity in oscillatory shear (η*) at 100 rad/sec at 190°C. Shear thinning may be characterized by the ratio of the Newtonianviscosity (η₀) to viscosity the complex viscosity at an arbitrarilychosen frequency of 100 rad/sec (η*₁₀₀). This η₀ may be measured invarious ways well known to those skilled in the art. Included amongthese are rotational oscillatory shear rheometry and rotational steadyshear rheometry, including shear creep. The value of η₀ may be obtainedfrom these methods by direct observation of the frequency independent orshear rate independent value of viscosity, or it may be determined froman appropriate fitting equation such as the Cross equation when the dataextend into the Newtonian region. Alternative data handling methodsincluded evaluating the limiting value of the ratio of the loss modulusto frequency, G″/ω, at low frequency:

η₀=lim G″/ω|_(ω→0),

or by linearly extrapolating the reciprocal of viscosity vs. shearstress to zero shear stress (e.g., G. V. Vinogradov, A. Ya. Malkin,Rheology of Polymers, Mir Publications Moscow, Springer-Verlag, p.153(1980)). Direct observation of the frequency independent value of thecomplex viscosity, η*, from rotational oscillatory shear and/or thefitting of the Cross equation to the same data were the methods used forthis description.

At low frequencies the melt viscosity expressed as the absolute value ofthe complex viscosity (η*) of high polymers is independent of thefrequency, i.e., it is constant with frequency and is called theNewtonian limiting viscosity, η₀. At increasing frequencies η* decreaseswith increasing frequency in a manner determined by its relaxationspectrum and this decrease in viscosity is called shear thinning (or,pseudoplasticity in earlier nomenclature). The plateau modulus may bedefined in several interrelated ways, e.g., the value of the storagemodulus (real part of the complex modulus), G′, in a region of G′constant with frequency, or the value of G′ at the frequency of aminimum in the loss modulus (imaginary part of the complex modulus), G″,or the value of G′ at the minimum in tan δ, where tan δ=G″/G′, or otherdefinitions which lead to similar answers. For purposes of thedescription we chose to use the ratio of the Newtonian viscosity to thecomplex viscosity as discussed above.

Definitions and description of these and other parameters discussed heremay be found, e.g., in Ferry (J. D. Ferry, Viscoelastic Properties ofPolymers, 3rd Ed., John Wiley & Sons, N.Y., 1980) and in Dealy andWissbrun (J. M. Dealy, K. F. Wissbrun, Melt Rheology and Its Role inPlastics Processing Theory and Applications, Van Nostrand Reinhold,N.Y., 1990). The methods of measurement, e.g., rotational oscillatoryshear between parallel circular plates in an instrument such as aRheometrics Scientific Mechanical Spectrometer, and data treatment,e.g., interconversion of complex variable Theological parameters andtime-temperature superposition, are also well known and frequently usedby those of ordinary skill in the art. Again, these are largelydescribed in the above references and in numerous other texts andpeer-reviewed publications in the field.

The ability of a polymer to exhibit strain hardening under extension(i.e., or increase of the extensional viscosity with strain rate) hasbeen shown to correlate with the melt strength of that polymer and theease of forming a bubble from it as in blown film operations inindustry. A measure of the strain hardening can be given as follows. Onecan predict what the extensional viscosity would be if the polymerobeyed linear viscoelasticity through the model of Chang and Lodge(Chang, H.; and Lodge, A. S.; Rheologica Acta, 11, pp. 127-129 (1972)).This is shown in the FIG. V as η_(ext)(linear). This can be compared tothe experimentally measured viscosity, called η_(ext) (measured) in thefigure. The sharp rise of η_(ext) (measured) over the predicted valueη_(ext)(linear) is the result of strain hardening. To extract a numberfrom the data that expresses the degree of this strain hardening, weselected the value of η_(ext) (measured) at conditions characteristic offilm blowing—a strain rate of 1 sect⁻¹, temperature of 190° C., and timeof 3 sec. The ratio then becomes the measured value divided by thatpredicted by the Chang and Lodge model at the same temperature and time.This ratio must be greater than 2 for clear evidence of strainhardening, so it can be represented as the following:

 ηext(measured)/η_(ext)(linear)≡η_(ext)ratio≧2.

Polymer melt elongation (or extension) is another important deformationin polymer processing. It is the dominant deformation in film blowing,blow molding, melt spinning, and in the biaxial stretching of extrudedsheets. Often, an extensional deformation producing molecularorientations takes place immediately before solidification resulting inanisotropy of the end-use properties. Extensional rheometry data arevery sensitive to the molecular structure of a polymer system therefore,these data is a valuable tool for polymer characterization.

The time dependent uniaxial extensional viscosity was measured with aRheometrics Scientific Melt Elongational Rheometer (RME). The RME is anelongational rheometer for high elongations of polymer melts. The sampleis supported by an inert gas, heated to the test temperature byelectrical heaters mounted in the side plates of the rheometer. Thetemperature is controlled from ambient to 350° C. The polymer meltsample is extended homogeneously by two metal belt clamps, eachconsisting of two metal belts with its fixtures. The metal belts controla range of extensional strain rates from 0.0001 to 1.0 s⁻¹. The forcesgenerated by the sample are measured by a spring type transducer with arange from 0.001 to 2.0 N. The maximum Hencky strain achievable by thisinstrument is 7 (stretch ratio=1100). This instrument is based upon apublished design, see Meissner, J., and J. Hostettler, Rheological Acta,33, 1-21 (1994), and is available from Rheometrics Scientific, Inc.

The rheological behavior of these polymers with controlled branchingshows surprising and useful features. These polymers have a zero-shearviscosity that is larger than a linear polymer of the same molecularweight. They show a rapid drop in viscosity with shear rate (largedegree of shear thinning); and a plateau modulus that is at least twotimes lower than that of prior art linear and branched polymers. Thislatter characteristic is especially surprising, since ethylene polymersof various types exhibit essentially the same plateau modulus. This wasthought to be intrinsic to the monomer type and not dependent on polymerarchitecture. The lower plateau modulus means that the comb polymerslikely are much less entangled than the linears, thus giving it such lowviscosity for their molecular weight. The utility of these properties ofthe invention polymers is that they have a very low viscosity for itsmolecular weights under melt processing conditions and so will processmuch more easily than the prior art polymers while exhibiting increasedextensional viscosity indicative of increased melt strength.

Polymer Preparation

Initial studies conducted to determine optimum polymer structuressuitable for the improved properties sought were based on knowledge asto production of hydrocarbon polymers with precisely controlledstructures through the saturation of anionically synthesized polydienes.Various polydienes can be saturated to give structures that areidentical to polyolefins as was reported by Rachapudy, H.; Smith, G. G.;Raju, V. R.; Graessley, W. W.; J. Polym. Sci.—Phys. 1979, 17, 1211. Thetechniques completely saturate the polydiene without any side reactionsthat might degrade or crosslink the molecules. The controlled molecularweight and structure available from anionic polymerization of conjugateddienes are thus preserved. A unit of butadiene that has beenincorporated 1, 4 into the polybutadiene chain will have the structureof two ethylenes (four methylenes) after saturation, and those that goin as 1, 2 will be like one butene unit. So the saturated versions ofpolybutadienes of a range of microstructures are identical in structureto a series of ethylene-butene copolymers. Similarly saturatedpolyisoprenes resemble an alternating ethylene-propylene copolymer, andother polydienes can give the structures of polypropylene and otherpolyolefins upon saturation. A wide variety of saturated hydrocarbonpolymers can be made in this way.

Thus linear ethylene-butene copolymers can be made by the saturation oflinear polybutadienes and linear ethylene-propylene copolymers of theinvention can be made by the saturation of linear polyisoprenes. Thelinear polymers can be prepared by anionic synthesis on a vacuum line inaccordance with the teachings of Morton, M.; Fetters, L. J.; RubberChem. & Technol. 1975, 48, 359. The polymers of the invention made inthis manner were prepared in cyclohexane at ˜0° C., with butyllithium asinitiator. The polydiene polymers were then saturated under H₂ pressureusing a Pd/CaCO₃ catalyst of J. Polym. Sci.—Phys. 1979, 17, 1211, above.This technique can be used to make polymers over a wide range ofmolecular weights, e.g. polymers with molecular weights from 3,500 to800,000.

The branched polymers of the invention can be made by attaching one ormore linear polymers, prepared as above, as branches to another of thelinear polymers serving as a backbone or main chain polymer. The generalmethod is to produce branch or arm linear polymers by the procedureabove, using the butyllithium initiator; this produces a polybutadienewith a lithium ion at the terminal end. A linear backbone is made in themanner described above, some number of the pendant vinyl double bonds onthe backbone polymers are then reacted with (CH₃)₂SiClH using a platinumdivinyl tetramethyl disiloxane catalyst. The lithium ends of the armpolybutadiene polymers then are reacted with the remaining chlorines onthe backbone polybutadiene vinyls, attaching the arms. Because both theplacement of the vinyl groups in the backbone and the hydrosilylationreaction are random, so is the distribution of arms along and among thebackbone molecules. These polybutadiene combs can be saturated as shownabove to form ethylene-butene copolymer combs with nearly monodispersebranches randomly placed on a nearly monodisperse backbone. Polymershaving two branches can be made by a similar synthetic procedure. Fouranionically synthesized polymers (arms) are attached to the ends of aseparately synthesized polymer (“connector”), two at each end. Thisresults in an H-shaped structure, i.e., a symmetric placement of thearms and non-random distribution of the of arms of the molecule.

An alternate method of preparing the branched olefin copolymers of theinvention, particularly ethylene copolymers, is by preparingolefinically unsaturated macromers having molecular weight attributeswithin that described for the branch or arm polymers or copolymers andincorporating those into a branched polymer by copolymerization. Suchcan be done, for example, by preparing branch macromers from olefinssuch that there is vinyl or vinylidene unsaturation at or near themacromer chain end. Such is known in the art and the teachings of thebackground art as to the use of metallocenes to prepare these macromers,and then to insert or incorporate the macromers into a forming polymeras long chain branches, are applicable in this regard. Each of U.S. Pat.No. 5,324,800 and international publication WO 94/07930 are incorporatedby reference for purposes of U.S. patent practice. Such can beaccomplished by the use of series reactions or in situ single processeswhere the selection of catalyst or catalyst mix allows for thepreparation of olefinically unsaturated macromers and subsequentincorporation of them into forming polymeric chains.

In order to assure the quality and number of branches sought, it issuitable to use a multistep reaction process wherein one or more branchmacromers are prepared and subsequently introduced into a reactionmedium with a catalyst capable of coordination copolymerization of boththe macromer and other coordination polymerizable monomers. The macromerpreparation preferably is conducted so as to prepare narrow MWDmacromers, e.g., 2.0-3.5, or even lower when polymerization conditionsand catalyst selection permit. The comonomer distribution can be eithernarrow or broad, or the macromer can be a homopolymeric macromer. Theuse of essentially single site catalysts, such as metallocene catalysts,permits of the sought narrow MWD. Branch separation, or statedalternatively, branch numbers by molecular weight of the backbone chain,is typically controlled by assuring that the reactivity ratios of themacromers to the copolymerizable monomers is in a ratio that allows thepreferred ranges for the branch structure as described above. Such canbe determined empirically within the skill in the art. Factors to beadjusted include: catalyst selection, temperature, pressure, and time ofreaction, and reactant concentrations, all as is well-known in the art.

In this manner, branched copolymers are made directly withouthydrogenation and the selection of comonomers is extended to the fullextent allowed by insertion or coordination polymerization. Usefulcomonomers include ethylene, propylene, 1-butene, isobutylene, 1-hexene,1-octene, and higher alpha-olefins; styrene, cyclopentene, norbornene,and higher carbon number cyclic olefins; alkyl-substituted styrene or;alkyl-substituted norbornene; ethylidene norbornene, vinyl norbornene,1,4-hexadiene, and other non-conjugated diolefins. Such monomers can behomopolymerized or copolymerized, with two or more copolymerizablemonomers, into either or both of the branch macromers or backbone chainsalong with the macromers. The teachings of co-pending U.S. provisionalpatent application 60/037323 filed Feb. 7, 1997, is incorporated byreference for purposes of U.S. patent practice. See also the examplesbelow where a mixed zirconocene catalyst was used in a fluidized gasphase polymerization of an ethylene-hexene copolymer product whichcontained component copolymer fractions meeting the limiting elements ofthe invention described herein.

INDUSTRIAL APPLICABILITY

The branched polyethylene copolymers according to the invention willhave utility both as neat polymers and as a portion or fraction ofethylene copolymer blend compositions. As neat polymers, the polymershave utility as film polymers or as adhesive components, the discussionof WO 94/07930 being illustrative. The fabricated articles of U.S. Pat.Nos. 5,272,236 and 5,278,272 are additionally illustrative.

The copolymers of the invention will also have utility in blends, thoseblends comprising the branched copolymer of the invention at from0.1-99.9 wt. %, preferably from 0.3-50 wt. %, more preferably 0.5-25 wt.%, and even more preferably 1.0-5 wt %, the remainder comprising anessentially linear ethylene copolymer of number-average molecular weightfrom about 25,000 Daltons to about 500,000 Daltons, typically thosehaving an MWD of from about 1.75-30, preferably 1.75-8.0, and morepreferably 1.9-4.0, with densities form 0.85 to 0.96, preferably 0.85 to0.93, as exemplified by the commercial polymers used for comparison inthis application. The blends in accordance with the invention mayadditionally comprise conventional additives or adjuvants inconventional amounts for conventional purposes. The blends according tothe invention exhibit improved processing, largely due to the inclusionof the branched ethylene copolymer according to the invention, and canbe more easily processed in conventional equipment.

EXAMPLES Example 1 Preparation of C1

A comb polybutadiene polymer (PBd) was prepared by couplinghydrosilylated polybutadiene backbone chains with polybutadienyllithiumsidechains, or branches. The polybutadiene which was used as backbonefor the hydrosilylation reaction was prepared by anionic polymerizationusing high vacuum techniques, with sec-BuLi in benzene at roomtemperature. (Characterization: M_(n)=106,500 by size exclusionchromatography (SEC) based upon a polybutadiene standard; 10% 1,2units). 10 grams of this backbone polymer chain were dissolved in 120 mltetrahydrofuran (THF) in an one-liter round bottom flask equipped with agood condenser, to which 3 drops of platinum divinyl tetramethyldisiloxane complex in xylene (catalyst, Petrarch PC072) were added. Thesolution was dried overnight with 1.5 ml trimethylchlorosilane, followedby the addition of 7.55 mmole dimethylchlorosilane. The mixture'stemperature was raised slowly to 70° C. Changing of the color, vigorousboiling and refluxing indicated the start of the reaction which wascontinued for 24 hours at 70° C. THF and chlorosilane compounds wereremoved in the vacuum line by heating the polymer at 45° C. for 5 days.The hydrosilylated polymer was freeze dried under high vacuum for 2days.

Living polybutadiene branch polymers (PBdLi, M_(n)=6,400 by SEC; T3)used for the coupling reaction was prepared in the same manner as thebackbone. The synthesis of PBdLi was performed by reacting 12.75 gramsof butadiene monomer with 2.550 mmoles of initiator. Prior to thecoupling reaction 1 gram of PBdLi was removed, terminated with methanoland used for characterization. 40% excess of PBdLi was used for thecoupling reaction, which was monitored by SEC and allowed to proceed for2 weeks. Excess PBdLi was terminated with methanol. The comb polymer wasprotected against oxidation by 2,6-di-tert-butyl-p-cresol and wasfractionated in a toluene-methanol system. Fractionation was performeduntil no arm or undesirable products were shown to be present by SEC.The comb was finally precipitated in methanol containing antioxidant,dried and stored under vacuum in the dark. Characterization, which wascarried out by SEC, membrane osmometry (MO), vapor pressure osmometry(VPO), low-angle laser light scattering (LALLS), and laser differentialrefractometry, indicated the high degree of molecular and compositionalhomogeneity. Molecular characterization results are shown in Table I.Using the M_(n) (MO, VPO) and M_(w) (LALLS) of Table I the number ofarms experimentally obtained is calculated, which is smaller than thetheoretically expected, indicating a small yield in the hydrosilylationreaction. Fractionation and characterization results are shown in TableI and II.

The number of branches, or sidechains, was determined by both ¹³C-NMRand ¹H-NMR. Resonances characteristic of methyl groups adjacent to a Siatom (at the point of connection to the backbone) was found from bothmethods: similarly, resonances characteristic of the methyl adjacent ofthe methine in a sec-butyl group (at the terminus of the arm from theinitiator used to polymerize it) was measured. From the combination ofthese methods, the number of arms per 10,000 carbons was found to be15±5, which is consistent with 34 arms for this example.

The resulting comb (branched polybutadiene polymer) (“C1”) was saturatedcatalytically. 3 grams of the comb polymer were dissolved in cyclohexaneand reacted with H₂ gas at 90° C. and 700 psi in the presence of 3 g ofa catalyst made by supporting Pd on CaCO3. The reaction was allowed toproceed until the H₂ pressure stopped dropping, or about 24h. Thepolymer solution was then filtered to remove the catalyst residues. Thesaturation of the polymer was seen to be greater than 99.5% by protonNMR. The polymer was thus converted by hydrogenation to anethylene-butene branched copolymer. See Tables I and II, below.

Example 2 Preparation of C2

8 grams of PBd (M_(n)=87,000 by MO, prepared as described in Example 1;BB₃) dissolved in 150 ml THF were hydrosilylated in the same manner asdescribed in Example 1, using 0.5 ml of trimethylchlorosilane and 2.43mmoles of dimethylchlorosilane. The hydrosilylated polymer was freezedried under high vacuum for 5 days. PBdLi (M_(n)=4,500 by VPO; T₅) wasprepared as described in Example 1 by reacting 11.5 grams of butadienewith 2.550 mmoles of initiator. 1 gram of T₅ was removed in order to beused for characterization purposes. The coupling reaction wasaccomplished as described in Example 1. Fractionation andcharacterization results are shown in Table I and Table II.

The resulting comb PBd (C2) was saturated catalytically as in Example 3.The saturation of the polymer was seen to be greater than 99.5% byproton NMR. The resulting saturated polymer had an M_(w) of 97,000 byLALLS.

Example 3 Preparation of C3

2 grams of PBd (M_(n)=108,000 by SEC, prepared as described in Example1; BB₄) dissolved in 50 ml THF were hydrosilylated in the same manner asdescribed in Example 1, using 0.5 ml of trimethylchlorosilane and 0.77mmoles of dimethylchlorosilane. The hydrosilylated polymer was freezedried under high vacuum for 2 days. PBdLi (M_(n)=23,000 by SEC; T₆) wasprepared as described in Example 1 by reacting 22 grams of butadienewith 0.936 mmoles of initiator. 1 gram of T₆ was removed in order to beused for characterization purposes. The coupling reaction wasaccomplished as described in Example 2. Fractionation andcharacterization results are shown in Table I and Table II.

The resulting comb PBd (C3) was saturated catalytically as in Example 3.The saturation of the polymer was seen to be greater than 99.5% byproton NMR. The resulting saturated polymer had an M_(w) of 598,000 byLALLS.

Example 4 Preparation of C4

6 grams of PBd (M_(n)=100,000 by SEC, prepared as described in Example1; BB₅) dissolved in 60 ml THF were hydrosilylated in the same manner asdescribed in Example 1, using 1.0 ml of trimethylchlorosilane and 3.83mmoles of dimethylchlorosilane. The hydrosilylated polymer was freezedried under high vacuum for 2 days. PBdLi (M_(n)=5,100 by SEC; T₇) wasprepared as described in Example 1 by reacting 27 grams of butadienewith 5.370 mmoles of initiator. 1 gram of T₇ was removed in order to beused for characterization purposes. The coupling reaction wasaccomplished as described in Example 2. Fractionation andcharacterization results are shown in Table I and Table II.

The resulting comb PBd (C4) was saturated catalytically as in Example 3.The saturation of the polymer was seen to be greater than 99.5% byproton NMR.

TABLE I Molecular characteristics of precursors and final polymers. 10⁻³M_(n) 10⁻³ M_(n) 10⁻³ M_(w) 10⁻³ M_(w) Part Sample (SEC)^(a) (MO)^(b)(LALLS)^(c) (VPO)^(d) M_(w)/M_(n) Backbone BB₂ 106.5 101 103 — 1.05 ArmT₃ 6.4 — — 6.5 1.03 Comb C1 — 274 — — 1.07 Backbone BB₃ 99.0 87 90.0 —1.04 Arm T₅ 4.8 — — 4.5 1.05 Comb C2 — 105.5 107 1.08 Backbone BB₄ 10897 104 1.05 Arm T₆ 23 23.5 1.04 Comb C3 — 612 1.07 Backbone BB₅ 100100.5 — — 1.04 Arm T₇ 5.1 — — 4.75 1.04 Comb C4 — 194 198 — 1.04 ^(a)THFat 30° C., Phenomenex columns (Type P Phenogel 5 linear, pore size: 50to 10⁶ Å). ^(b)Toluene at 35° C., Model 231, Wescan. ^(c)Cyclohexane at30° C., KMX-6, Chromatix. ^(d)at 50° C., Model 833, Jupiter InstrumentCompany.

TABLE II Number of arms Comb Maximum possible^(a) Calculated^(b)Measured^(d) Yield (%) C1 100 29^(c) 34 29-34 C2 — 3.9 2.4 — C3 — 22^(c)— — C4 — 19^(c) — — ^(a)From total number of pendant vinyl groups.^(b)Calculated from M_(n) by MO and VPO. ^(c)Calculated from Mw byLALLS. ^(d)Measured by ¹³C-NMR.

Example 5 Preparation of Blend 1

Blend 1:6.8685 g of EXCEED® 103 (“ECD103”), a commercially availableethylene-1-hexene linear low density polyethylene of Exxon Chemical Co.having a density of 0. 917 and MI of 1.0, and 0.1405 g of C1 (above)were dissolved in 100 ml of xylene at 130° C. 0.0249 g of a stabilizerpackage (a 1:2 mixture of Irganox® 1076 and Irgafos®168 from Ciba-Geigy,Inc.) was also added. The solution was allowed to mix for 2 hours at130° C., and then the polymer blend was precipitated by adding thexylene solution to 1800 ml of methanol chilled to 2° C. The precipitatewas washed with more methanol, and the remaining xylene was removed bydrying in a vacuum oven at 88° C. for two days.

Example 6 Preparation of Blend 2

Blend 2:6.8607 g of the EXCEED® 103 (ECD103), 0.1402 g of C3 (above) and0.0248 of the stabilizer package were mixed in the same manner as Blend1.

H-shaped Polymer Examples Example 7 Preparation of H1

Preparation of arms:

6.3 ml (5.0 g) 1,3-butadiene was diluted in 75 ml benzene (6.1% w/v). Tothis solution was added 16.3 ml sec-BuLi 0.062M in n-hexane (1.01×10⁻³mol sec-BuLi). After 24 h at room temperature the reaction was complete.1.0 g of the product polybutadiene (Y; M_(n)=5,500 by SEC) in 18 mlsolution was removed for the characterization procedure and the rest ofY was mixed with 8.3 ml CH₃SiCl₃0.046 M in benzene (0.38×10⁻⁴ mol CH₃SiCl₃). After 7 days at room temperature the reaction was complete andthe Y₂Si(CH₃)Cl was formed.

Preparation of connector:

A difunctional initiator was prepared by the addition of sec-butyllithium to 1,3-bis(1-phenyl ethenyl) benzene, resulting in1,3-bis(1-phenyl-3 methyl pentyl lithium) benzene, called here DLI. 15.4ml (11.4 g) 1,3-butadiene was diluted in 355 ml benzene (2.3% w/v). Tothis solution was added 33.8 ml of DLI 0.0225M in benzene (7.3×10⁻⁴ molDLI) and 8.4 ml of sec-BuOLi 0.10M in benzene (8.36×10⁻⁴ mol sec-BuOLi).After 4 days at room temperature the reaction was complete. 1.0 g of theproduct difunctional polybutadiene (X; M_(n)=27,100 by SEC; M_(w)=24,500by LALLS) in 35 ml solution was removed for the characterizationprocedure. 4.8 g of X in 175 ml solution was removed for the formationof the Y₂Si(CH₃)X(CH₃)SiY₂.

Formation of H1:

4.0 g of Y₂Si(CH₃)Cl and 34.8 g of X were mixed. To the solution wasadded 1.0 ml THF. After 7 days at room temperature the formation of theH1 was complete. H1 comprised a structure having a backbone of about38,000 M_(n) plus two Y arms and of about 5,500 M_(n) (Y arms).

Fractionation:

The product of the previous reaction was precipitated in 1000 mlmethanol and was redissolved in 900 ml toluene (1% w/v). 450 ml methanolwas added and the solution was stirred at room temperature to reach thecloud-point. After that 20 more ml of methanol were added and thetemperature was increased slowly, until the solution became clear. Thenit was left to cool down and next day the separated part of the H1 wascollected, as the lower phase in a two-phase system. To the upper phasewas added 25 ml methanol, to reach again the cloud-point and then 20 mlmore methanol. The temperature was increased slowly and after theclearance of the solution, it was left to cool down. The newly separatedpart of the H1 was mixed with the previous part from the firstfractionation and it composed the final pure H1. By LALLS the H1 had anM_(w) of 50,000.

Saturation:

The H1 was saturated in the same manner as in Example 3, except that 0.2g of triphenyl phosphate and 0.0366 g of tris(triphenylphosphine)rhodium(I)chloride were added to the reaction for every gramof polymer. Essentially complete saturation was achieved. The resultingsaturated polymer had an M_(w) of 48,000 by LALLS.

Example 8 Preparation of H2

Preparation of Arms:

9.0 ml (6.7 g) 1,3-butadiene was diluted in 65 ml benzene (10.3% w/v).To this solution was added 10.7 ml sec-BuLi 0.062M in n-hexane(6.66×10⁻⁴ mol sec-BuLi). After 24 h at room temperature the reactionwas complete. 1.0 g of the product polybutadiene (Z; M_(n)=11,000 bySEC; M_(w)=10,800 by LALLS) in 13 ml solution was removed for thecharacterization procedure and the rest of Z was mixed with 5.8 ml ofCH₃SiCl₃ 0.046M in benzene (0.27×10⁻³ mol CH₃SiCl₃). After 7 days atroom temperature the reaction was complete and the Z₂Si(CH₃)Cl wasformed.

Preparation of connector:

3.4 g of X in 125 ml solution was removed for the formation of theZ₂Si(CH₃)X(CH₃)SiZ₂ (H2) in the manner of Example 7.

Formation of H2:

5.7 g Of Z₂Si(CH₃)Cl and 3.4 g of X were mixed. To the solution wasadded 1.0 ml THF. After 7 days at room temperature the formation of theH2 was complete. H2 had a resulting H-shaped structure like H1.

Fractionation:

The procedure followed was the same as in Example 7. The resultingpolymer had an M_(w) of 67,000 by LALLS.

Hydrogenation:

The procedure followed was the same as in Example 7. The resultingsaturated polymer had an M_(w) of 64,700 by LALLS.

Rheological Properties of Examples

The melt shear rheological behavior of the various resulting copolymerexamples was measured by well known methodology, i.e., rotationalsinusoidal oscillatory shear between parallel plates in a RheometricsScientific RMS-800 Mechanical Spectrometer. Frequency ranges of from 0.1to 100 rad/sec or from 0.1 to ca. 250 rad/sec or from 0.1 to ca. 400rad/sec or from 0.01 to 100 rad/sec or from 100 to 0.01 rad/sec werecovered at a sequence of temperatures ranging from 120° C. to 250° C.and in some cases to as high as 330° C. Typically, the examples weretested at isothermal conditions from 0.1 to 100 rad/sec or to ca. 250rad/sec at 120° C., 150° C., 170° C., 190° C., and 220° C.,successively, and then from 0.01 to 100 rad/sec at 250° C., 280° C. orhigher as necessary to access the terminal linear viscoelastic regime.Repeat testing was periodically performed on the same specimens at 150°C. (sometimes at 220° C.) to check reproducibility. All measurementswere performed at strains within the linear viscoelastic regime, andeither one or two specimens were used to cover all temperatures tested.The parallel plates were 25 mm in diameter and the gap between theplates (sample thickness) was precisely set at values from ca. 1.6 mm to2.3 mm for different test specimens and temperatures. Use of successivetemperature testing on single specimens requires compensation fortooling expansion with increasing set temperature in order to maintainconstant gap distance at all temperatures. This was accomplished in allcases by raising the upper platen (plate) at each new increasedtemperature by the amount 0.0029 mm/° C. Additionally, in some casessample expansion evidenced by normal stress increase was compensated bymaintaining a constant (low) normal stress in the sample at the varioustemperatures. The above methods are all well known to practicingrheologists. All samples were stabilized by addition of 1% (wt) of a 1:2mixture of Irganox® 1076/Irgafos® 168 (Ciba-Geigy, Inc.) prior tocompression molding test specimens in a Carver Laboratory Press.

The resultant linear viscoelastic data, which may be expressed innumerous ways, but here were expressed as complex viscosity, η*, elasticstorage modulus, G′, loss modulus, G″, and complex modulus, G*, werethen superimposed to the 190° C. reference temperature by well knowntime-temperature superposition methodology, yielding master curves ofthe above parameters vs. frequency over up to seven orders of magnitudeof frequency from the terminal regime through the rubbery plateau region(where possible). Superposition specifically was performed by verticalshifting of the logio complex modulus according to the equation

b_(T)=ρ_(o)T_(o)/ρT

where b_(T) is the vertical shift factor, ρ is the melt density attemperature, T's are absolute temperatures in °K, and the subscript, o,refers to the 190° C. reference temperature. Vertical shifting wasfollowed by arbitrary horizontal shifting of log₁₀ complex modulus alongthe log₁₀ frequency axis to yield the horizontal shift factors, a_(T),which were then fitted to an Arrhenius form equation to yield the energyof activation for viscous flow, E_(a), where E_(a) is derived from

a_(T)=exp[(E_(a)/R)(1/T−1/T_(o))]

and where R=1.987×10⁻³ in kcal/mol °K

The following critical melt shear rheological attributes at 190° C.,derived from the master curve data, describing aspects of the inventionare given in Tables III and VI for each of the examples:

Newtonian viscosity, η₀, in Pa-s

Plateau modulus, G_(N) ⁰, in Pa (evaluated at the frequency ofG″minimum)

Ratio of Newtonian value to viscosity at 100 rad/sec, η 0 /η*_((100s)_(⁻¹) ₎,

Ratio of the extensional viscosity measured at a strain rate of 1 sec⁻¹,190° C., and time=3 sec (i.e., a strain of 3) to that predicted bylinear viscoelasticity at the same temperature and time, and

Energy of activation, E_(a).

The high Newtonian viscosities of the invention indicate advantageouslyhigh extensional viscosities (at low strain rate). The low plateaumoduli of the invention, as well as the measures of shear thinning, areindicative of low viscosity at, e.g., extrusion, blow molding, andinjection molding shear rates.

Example 1-1 (C1)

C1 was ground into coarse powder and dry mixed with 1%(wt) of a 1:2mixture of Irganox® 1076/Irgafos® 168 (Ciba-Geigy, Inc.). This materialwas then compression molded into 1 inch (25.4 mm) diameter×2 mmthickness disks in a Carver Laboratory Press (Fred S. Carver, Inc.)using a cavity of these dimensions and Teflong coated aluminum sheetliners. Molding was performed at ca. 190° C. and 10,000 psi. The meltlinear viscoelastic testing as a function of frequency was performed atthe various temperatures given below on two such specimens in aRheometrics Scientific RMS-800 Mechanical Spectrometer in parallel platesinusoidal oscillatory shear mode. Plate diameters and specimendiameters at test conditions were 25 mm and gap setting (samplethickness) at the initial 150° C. was 1.865 mm. Measurements were madeon a single specimen at 150° C. (0.1-251 rad/sec, 1.865 mm gap), 120° C.(0.1-251 rad/sec, 1.865 mm gap), 170° C. (0.1-251 rad/sec, 1.908 mmgap), 190° C. (0.1-158 rad/sec, 1.993 mm gap), and 220° C. (0.1-251rad/sec, 2.071 mm gap). On a second specimen, measurements were thenperformed at 220° C. (0.1-251 rad/sec, 2.081 mm gap), 250° C. (0.01-100rad/sec, 2.111 mm gap), and 220° C. (100-0.01 rad/sec, 2.081 mm gap).Maintaining the gap setting constant with increasing temperature at thelower temperatures was accomplished compensating for tooling thermalexpansion/contraction as described in the general section above. Theincreased gap setting at higher temperatures compensated both fortooling dimension change and for sample expansion, where the latter wasaccomplished by maintaining a constant (low) normal stress on thesample.

The resultant melt rheological parametric data were expressed asdescribed in the general section above and were superimposed to 190° C.reference temperature master curves covering seven decades of reducedfrequency in the well known manner described above using IRIS computersoftware (IRIS version 2.5, IRIS Development, Amherst, Mass.). Specificvalues of the parameters, Newtonian viscosity, plateau modulus, ratio ofthe Newtonian viscosity to the viscosity at 100 rad/sec, and energy ofactivation for viscous flow, are given in Table III.

FIGS. 1-4 illustrate the surprising features of the C1 as compared tothose of commercial low density and linear low density polyethylenepolymers. G28

FIG. 1 shows that the invention C1 exhibited a stronger frequencydependence of the viscosity than any of the comparative examples A, B,C, and D. This translates into lower energy input per throughput unitfor the invention polymer. Note, this plot is dependent on thetemperature and molecular weight of the example polymers, in addition toMWD and molecular architecture.

FIG. 2 is a plot of these variables in a reduced variable manner thatrenders viscosity curves which are independent of the temperature andthe magnitude of the molecular weight, hence the comparison was made onequal footing. The differences were only due to the MWD and thebranching characteristics. Note that the reduced viscosities of the twoLDPE examples (A & B) were on top of each other. As for FIG. 1, thisplot clearly shows that for high throughputs, as desired in meltprocessing, the invention Example I exhibited lower values of theviscosity than any of the comparative examples (A, B, C, & D). Thistranslates into lower energy requirements per throughput unit.

FIG. 3 shows that C1 exhibited a region over which G′ was essentiallyfrequency independent, which can be taken as the plateau modulus. Thebehavior of the storage modulus of the comparative examples showed eachto increase with the frequency, even after the frequency at which theinvention reached a plateau. As with FIG. 1 the effects of the molecularweight and temperature have not been removed.

FIG. 4 shows the storage modulus of the example polymers against theproduct of the zero shear viscosity and frequency, thus removing theeffects of temperature and molecular weight. Accordingly this plotreflects only the influence of the MWD and branching characteristics onthe behavior of the storage modulus. This plot unquestionably shows thatthe storage modulus of Example I reached the rubbery plateau regionwhereas the storage moduli of the comparative examples were stillincreasing with frequency.

Example 2-1 (C2)

A single test specimen of C2 was prepared with stabilization andcompression molding as described in the general discussion above andtested at the sequence of temperatures, 150° C. (0.1-100 rad/sec, 1.221mm gap) 120° C. (0.1-100 rad/sec, 1.221 mm gap), 170° C. (0.1-100rad/sec, 1.221 mm gap), 190° C. (100-0.01 rad/sec, 1.221 mm gap), 220°C. (100-0.01 rad/sec, 1.221 mm gap), and 150° C. (0.1-100 rad/sec, 1.221mm gap). The resultant melt rheological parametric data were expressedas described in the general section above and were superimposed to 190°C. reference temperature master curves covering six to seven decades ofreduced frequency in the well known manner described above using IRIScomputer software (IRIS version 2.5, IRIS Development, Amherst, Mass.).Specific values of the parameters, Newtonian viscosity, plateau modulus,ratio of the Newtonian viscosity to the viscosity at 100 rad/sec, andenergy of activation for viscous flow, are given in Table III.

Example 3-1 (C3)

A single test specimen of C3 prepared as in Example 2-1 was tested at asequence of temperatures ranging from 120° C. to 330° C. with repeattests at 150° C. performed after the 250° C. and the 300° C. tests. Thefrequency ranges at the individual temperatures were as described in thegeneral description of methodology above. The resultant melt rheologicalparametric data were expressed as described in the general section aboveand were superimposed to 190° C. reference temperature master curvescovering seven to eight decades of reduced frequency by the methodsdescribed in Examples 1-1 and 2-1 Specific values of the parameters,Newtonian viscosity, plateau modulus, ratio of the Newtonian viscosityto the viscosity at 100 rad/sec, and energy of activation for viscousflow, are given in Table III.

Examples 4-1 through 8-1 (C4, Blend 1, Blend 2, H1, H2)

Examples 4-1 through 8-1 were prepared and tested variously within thegeneral methodology described in the above sections. The data from thevarious temperatures for each example were superimposed to 190° C.master curves as described in Example 1-1. Specific values of theparameters, Newtonian viscosity, plateau modulus, ratio of the Newtonianviscosity to the viscosity at 100 rad/sec, and energy of activation forviscous flow, are given in Table III. Where specific values are omitted,they could not be determined with reasonable certainty from the data.

Example 9-1 (ECD103) (Comparative)

Example 9-1 was linear polyethylene used in the blends, Examples 5-1 and6-1. It was stabilized as described in the general method descriptionand compression molded into a 2.5 in.×2.5 in.×2 mm plaque from whichthree 25 mm diameter×2 mm thickness disks were cut. Melt viscoelastictesting was performed on the first specimen from 0.1 to 400 rad/sec atthe succession of temperatures, 130° C., 120° C., 115° C., 150° C.Subsequently tests were performed on separate specimens from 0.1 to 100rad/sec at 170° C. and at 190° C. Data superposition to 190° C. mastercurves was performed as described in previous examples, and specificvalues of the parameters, Newtonian viscosity, plateau modulus, ratio ofthe Newtonian viscosity to the viscosity at 100 rad/sec, and energy ofactivation for viscous flow, are given in Table III. Where specificvalues are omitted, they could not be determined with reasonablecertainty from the data.

Sample Preparation For Extensional Rheology

Samples identified in Tables III and VI were tested in a RheometricsPolymer Melt Elongational Rheometer (RME) for the value of the η_(ext)ratio . They prepared as rectangular parallelepipeds whose length, widthand thickness are approximately 60, 8, and 1.5 mm, respectively. Thesesamples were prepared by compression molding the polymer of interestwithin a brass mask.

The first step in the procedure used to mold these samples was to weighout approximately 0.9 g of polymer, which was sufficient to completelyfill the mask. When the bulk material was in pellet or powder form, theweighing process was straightforward. However, when the material to betested was received in hard chunks, an Exacto knife was used to cutsmall pieces of polymer from the bulk until the aforementioned mass hadbeen collected. The next step was to stabilize the polymer, which wasonly necessary for those materials that were not in pelletized form.This was accomplished by adding one weight percent IRGAFOS® 168stabilizer (Ciba-Geigy, Inc.) to the weighed out polymer. The brassextrusion die was then filled with the stabilized polymer, andsandwiched between heated platens at 190° C. that are mounted on ahydraulic press (Carver Inc.) The purpose of the die is to mix themelted polymer so that the resulting test specimens are free of airbubbles and weld lines. The presence of either can cause the testspecimen to break at lower total strains versus the case in which thepolymer chains of the test specimen are fully entangled. Note that1″×1″×{fraction (1/16)}″ sheets of mylar were used to cap the die inorder to keep the polymer within the die from contacting and sticking tothe platens.

Once the polymer had melted within the die, the bottom sheet of mylarwas removed, and the plunger was placed into the hole of the die. Thebrass mask was then mounted onto the bottom platen, with a sheet ofmylar (3″×2″×{fraction (1/16)}″) being placed between the mask and theplaten. The die and plunger were then placed onto the brass mask, sothat the hole of the die coincided with the geometric center of the maskslit. The polymer was then extruded into the mask by closing the platensof the press, which drove the plunger into the die. The mask and diewere then removed from the press and allowed to cool to approximately100° C. at which point the mask was separated from the die. Because thesample held within the mask is not dimensionally homogeneous afterextrusion, it was remolded within the press at 190° C. and 2000 psibetween two 4″×2″×{fraction (1/16)}″ mylar sheets. After applying heatto the sample and mask for approximately ten minutes, the power to theplaten heaters was turned off, and the sample and mask were allowed tocool to room temperature (approximately 2 hours). It was necessary toslowly cool the polymer specimen in this way so that the molded samplewas free of residual stresses. Finally, the specimen was carefullyremoved from the mask. its dimensions were measured, and it was testedwithin the RME.

Sample Testing in the Rheometrics Polymer Melt Elongational Rheometer(RME)

After allowing for the oven of the RME to heat up to the desired testingtemperature, calibration of the force transducer was performed. This wasaccomplished with the rotary clamps (with stainless steel belts)installed, and the top clamp on the transducer side (right-hand side) ofthe oven in the lowered position. With no mass hanging from thetransducer shaft and pulley located at the back of the oven, the forcecalibration window was brought up in the data acquisition software.After choosing the desired force scale, the force gain was set to unity,and offset values were input until the average force readout on thescreen was zero. A mass corresponding to that chosen for the force scalewas then attached to the transducer shaft and hung over the pulley. Thegain in the calibration window was then adjusted until the averagemeasured force was equal to the mass attached to the transducer. Oncethis was accomplished, the mass was removed from the shaft/pulley andthe offset in the force calibration window was adjusted until me averagemeasured force. was again zero. The mass was then re-attached and thegain was readjusted until the proper force readout was achieved. Thisprocedure of zeroing and scaling the transducer readout was repeatediteratively until values for the offset and gain in the calibrationwindow of the data acquisition software were obtained thatsimultaneously yielded a zero force when the transducer shaft was loadfree and the proper force for the attached mass.

After calibrating the force transducer and measuring the dimensions ofthe parallelepiped test specimen, the temperature within the oven waschecked to ensure that the oven was at the appropriate test temperature.The valve on the gas flow regulator was then turned 180° so that 99.6%pure nitrogen was delivered to the oven for temperature control. Afterwaiting for the oven to be flooded with nitrogen gas (2-3 minutes), thespecimen was loaded between the rotary clamps using the RME loadingblock (i.e. the top clamps are in locked or upper position). Typically,16 (cm³/min) of gas were delivered to the air table, while 14 (cm³/min)were used to heat the rotary clamps. During loading it was important forthe specimen not to touch the top of the air table, because this cancause the specimen to stick and an extra force will be measured duringelongational testing.

Immediately after releasing the specimen above the air table, theright-hand clamp was lowered to hold the specimen in place The samplewas then allowed to melt, while being levitated over the table forapproximately 5-6 minutes. The left-hand rotary clamp was then closed,and the specimen was checked to insure that it did not stick to the airtable. Generally, the melted specimen had sagged somewhat between thetable and the clamps, which can cause some sticking to the air table anderroneous force data at low strains. To overcome this problem, the slackwas drawn up by jogging the clamps at an angular velocity of 1 rev/min.Sample testing was then initiated by setting the VCR to record mode,initiating the video timer, and choosing start test in the dataacquisition software, respectively. Subsequent to the sample beingelongated, the valve on the gas flow regulator was returned to the airside, and the required test parameters were entered into the dataacquisition software. The rotary clamps and oven door were then opened,and the clamps were removed. Finally, the tested polymer was extractedfrom the stainless steel belts, and recycled for additional elongationaltests.

TABLE III 190° C. SHEAR RHEOLOGY and EXTENSIONAL RHEOLOGY EXAMPLES η₀(190° C.) Linear η₀ Equivalent G_(N) ⁰ η₀/η* E_(a) EXAMPLE (Pa − s) (Pa− s) (Pa) η_(ext) ratio (100 s⁻¹) (kcal/mol) MULTIPLY BRANCHED (>2)STRUCTURES 1 (C1) 1.0 × 10⁶ 1.0 × 10⁵ 1.3 × 10⁵  — 710 18.4 2 (C2)   9 ×10⁵ 4.5 × 10³ ˜6 × 10⁵ — 130 15.0 3 (C3) >5 × 10⁷  1.6 × 10⁶ ˜3 × 10⁴— >1200 17.6 4 (C4) >1 × 10⁷  3.5 × 10⁴ ˜3 × 10⁵ — >2500 17.0 (Noterminal region) 5 (BLEND 1) 7.5 × 10³ — — 2.25 3.2 7.88 (2% C1/98%ECD103) (Rubbery plateau not accessed) 6 (BLEND 2)   8 × 10³ — — 3.183.3 8.54 (2% C3/98% EDC103) (Rubbery plateau not accessed) H-STRUCTURES7 (H1) 6.4 × 10³ 3.0 × 10²   5 × 10⁵ — 2.4 12.2 8 (H2) 6.4 × 10⁴ 8.2 ×10² ˜3 × 10⁵ — 26 15.8 LINEAR ( (ECD103) (Comparative) 6.7 × 10³ 8.3 ×10³ — 1.48 2.7 7.86 NOTES: G_(N) ⁰ was evaluated as the value of G′ atthe frequency of G″ minimum. For comparison, the η₀ for a linearequivalent (same M_(w)) polymer is shown in col. 2 using the equation η₀(190° C.) = 5.62 × 10⁻¹⁴ M_(w) ^(3.36) (Pa − s) derived from Eq. 16,Mendelson, et al, J. Poly. Sci., Part A, 8, 105-126. (1970).

Example 10 In situ Mixed Zirconocene Catalyst Example

This example illustrates the preparation of branched copolymers via anin situ coordination polymerization method using a mixed zirconocenecatalyst as described in U.S. Pat. No. 5,470,811.

1) Preparation of Mixture of Isomers of (MeEtCp)₂ZrCl₂[bis(1,2-MeEtCp)ZrCl₂, bis(1,3-MeEtCp)ZrCl₂, and (1,2-MeEtCp)(1,3-MeEtCp)ZrCl₂, where Me=methyl, Et=ethyl, Cp=cyclopentadienyl],Hereinafter Called (1,2/1,3-MeEtCp)₂ZrCl₂:

Methylcyclopentadiene dimer was cracked to the monomeric units over highviscosity silicone oil. A sample of the freshly preparedmethylcyclopentadiene (100.5 g, 1.26 mol) was diluted in 500 cm³tetrahydrofuran in a 3-liter flask. The flask was cooled in an ice-bathto 0° C. and 900 cm³ of 1.4 M solution of methyllithium in hexane wasadded slowly. After complete addition of the MeLi the ice-bath wasremoved and stirring continued for 3 hours at room temperature. Then theflask was cooled again to 0° C. and bromoethane (139.2 g, 1.28 mol) wasadded slowly as solution in THF. The mixture was then stirred for 15hours. The resulting product was washed with distilled water and theorganic layer was dried over sodium sulfate. This was then filtered andconcentrated under vacuum and the concentrate was dissolved with agentle N₂ sparge. The fraction boiling between 118-120° C. was saved.

Freshly distilled methylethyl-cyclopentadiene isomers (41.9 g, 0.388mol) as above was dissolved in 30 cm³ THF. 242 cm³ of 1.6 M solution ofn-BuLi in hexane was slowly added to this and stirring was continued for3 hours after all the n-BuLi had been added. This solution was thenadded slowly to a slurry of ZrCl₄ (45.2 g; 0.194 mol.) in 200 cm³ THIFat −80° C. Stirring continued for 15 hours as the temperature slowlywarmed up to 20° C. The solvent was removed under vacuum and the solidrecovered was extracted with toluene. The toluene extract wasconcentrated and pentane was added to aid precipitation of the purecompound at −30° C.

2.) Preparation of Mixed Zirconocene Catalyst:

2300 g of Davison 948 silica dried at 200° C. was slurried in 6000 cm³heptane in a reaction flask. The flask was maintained at 24° C. and 2500cm³ of 30 wt % methylalumoxane in toluene was added. After 0.5 hours,the temperature was raised to 68° C. and maintained for 4 hours. Then atoluene solution of 24.88 g (1,3-MeBuCp)₂ZrCl₂ (where Bu is butyl),mixed with 21.64 g of the isomeric mix (1,2/1,3-MeEtCp)₂ZrCl₂, preparedabove, was added slowly followed by a 1 hour hold of the reactionconditions. Then the resultant catalyst was washed with hexane 4 timesand then dried to a free-flowing powder with a gentle N₂ flow.

Fluidized-Bed Polymerization. The polymerization was conducted in acontinuous gas phase fluidized bed reactor. The fluidized bed was madeup of polymer granules. The gaseous feed streams of ethylene andhydrogen together with liquid comonomer were mixed together in a mixingtee arrangement and introduced below the reactor bed into the recyclegas line. Hexene was used as comonomer. Triethyl aluminum (TEAL) wasmixed with this stream as a 1% by weight solution in isopentane carriersolvent. The individual flow rates of ethylene, hydrogen and comonomerwere controlled to maintain fixed composition targets. The ethyleneconcentration was controlled to maintain a constant ethylene partialpressure. The hydrogen was controlled to maintain a constant hydrogen toethylene mole ratio. The concentration of all the gases were measured byan on-line gas chromatograph to ensure relatively constant compositionin the recycle gas stream.

The solid catalyst (above) was injected directly into the fluidized bedusing purified nitrogen as a carrier. Its rate was adjusted to maintaina constant production rate. The reacting bed of growing polymerparticles was maintained in a fluidized state by the continuous flow ofthe make up feed and recycle gas through the reaction zone. Asuperficial gas velocity of 1-2 ft/sec was used to achieve this. Thereactor was operated at a total pressure of 300 psig. To maintain aconstant reactor temperature, the temperature of the recycle gas wascontinuously adjusted up or down to accommodate any changes in the rateof heat generation due to the polymerization.

The fluidized bed was maintained at a constant height by withdrawing aportion of the bed at a rate equal to the rate of formation ofparticulate product. The product was removed semi-continuously via aseries of vanes into a fixed volume chamber, which was simultaneouslyvented back to the reactor. This allowed for highly efficient removal ofthe product, while at the same time recycling a large portion of theunreacted gases back to the reactor. This product was purged to removeentrained hydrocarbons and treated with a small stream of humidifiednitrogen to deactivate any trace quantities of residual catalyst.

TABLE IV Polymerization Run Conditions Metallocene Catalyst¹ mixed ZrBed Weight (kg) 110 Zr (wt %) 0.58 TEAL Bed Concentration 49 (ppm) Al(wt %) 14.92 Catalyst Productivity 3900 (kg/kg) Al/Zr (mole/mole) 87Bulk Density (g/cc) 0.456 Temperature (° C.) 78.9 Average Particle Size777 (microns) Pressure (bar) 21.7 Melt Index (dg/min) 0.83 Ethylene(mole pct) 50.2 Melt Index Ratio 21.5 Hydrogen (mole ppm) 147 Density(g/cc) 0.9166 Hexene (mole pct) 1.13 Production rate (kg/hr) 33 ¹See,Example 1-1.) and 1-2 .) catalyst preparation above.

Mixed Zirconocene Catalyst Copolymer (“EXP 10”)

This experimental copolymer was an ethylene-hexene copolymer producedwith the mixed zirconocene catalyst described above. This example hadthe following properties: 0.9187 g/cc density, 0. 91 dg/min I₂, 6.53dg/min I₁₀, 21.1 dg/min I₂₁, 7.18 I₁₀/I₂, 23.2 I₂₁/I₂, 31,900 M_(n),98,600 M_(w), 23,1700 M_(z), 3.08 M_(w)/M_(n), 2.35 M_(z)/M_(w), and10.9 cN melt strength.

Commercial Resins

Comparative Ex. A is ESCORENE® LD-702 from Exxon Chemical Co., acommercial ethylene-vinyl acetate copolymer (LDPE film resin) having aMelt Index of 0.3 g/10 min. a density of 0.943 and a vinyl acetatecontent of 13.3 wt. %. Comparative Ex. B is ESCORENE® LD-113 from ExxonChemical Co., a commercial homopolyethylene polymer (LDPE packagingresin) having a Melt Index of 2.3 g/10 min. and a density of 0.921.Comparative Ex. C is EXCEED® 399L60 from Exxon Chemical Co., acommercial ethylene-hexene copolymer (LLDPE blown film resin) having aMelt Index of 0.75 g/10 min. and a density of 0.925. Comparative Ex. Dis AFFINTY® PL-1840 from The Dow Chemical Company, a commercialethylene-octene copolymer (LLDPE blown film resin) having a Melt Indexof 1.0 g/10 min. a density of 0.908 and an octene content of 9.5 wt.%.Comparative Ex. E is ELVAX® 3135 from DuPont Co., a commercialethylene-vinylacetate copolymer (EVA resin for blown film/flexiblepackaging applicatioins ) having Melt Index of 0.3g/10 min. and a vinylacetate content of 12 wt %.

Test Methods

Melt Index (I₂) of the resin samples was determined according toASTM-D-1238, Condition E. Melt Flow Rate with a 10 kg top load (I₁₀ wasdetermined according to ASTM-D-1239, Condition N. Melt Flow Rate with a21.6 kg top load (I₂₁) was determined according to ASTM-D1238, conditionF. Density of the resin samples was determined according to ASTM-D-1505.Bulk Density: The resin was poured via a ⅞″ diameter funnel into a fixedvolume cylinder of 400 cc. The bulk density is measured as the weight ofresin divided by 400 cc to give a value in g/cc. Particle Size: Theparticle size was measured by determining the weight of materialcollected on a series of U.S. Standard sieves and determining thenumber-average particle size based on the sieve series used.

Description of Supercritical Fractionation

The use of supercritical fluids as solvents allows for the fractionationof polymers by either molecular weight or composition. For example,supercritical propane is a good solvent for polyethylene and otherpolyolefins (homo- and copolymers) at high enough pressure andtemperature. If the temperature is kept constant and is high enough sothat the polymer is totally non-crystalline, then one can fractionatethe sample by molecular weight by varying the pressure. The criticalpressure for solubility (that is, the pressure below which the polymeris no longer soluble in the supercritical propane) increases withmolecular weight, so that as the pressure is dropped from some largevalues the higher molecular weight fractions will drop out of solutionfirst, followed by progressively smaller molecular weight fractions asthe pressure is lowered (Watkins, J. J.; Krukonis, V. J., Condo, P. D.;Pradhan, D.; Ehrlich, P.; J. Supercritical Fluids 1991, 4, 24-31). Onthe other hand, if the pressure is held constant and the temperature islowered, then the most crystallizable portions of the polymer will comeout first. Since for ethylene-α-olefin copolymers the crystallizabilityis generally controlled by the amount of ethylene in the chain, such anisobaric temperature profiling will fractionate the sample bycomposition (Watkins, J. J.; Krukonis, V. J.; Condo, P. D.; Pradhan, D.;Ehrlich, P.; J Supercritical Fluids 1991, 4, 24-31; Smith, S. D.;Satkowski, M. M.; Ehrlich, P.; Watkins, J. J.; Krukonis, V. J.; PolymerPreprints 1991, 32(3), 291-292). Thus, one has the option offractionating by either molecular weight or composition from the samesupercritical solution, by varying either pressure or temperature,respectively. In the samples used herein, we chose to obtain fractionsof various molecular weights by isothermal pressure variation.

Supercritical Fractionation Example

100 grams of EXP10 resin was fractionated using a supercritical propanesolution in the manner described above. This was carried out by PhasexCorp., 360 Merrimack St., Lawrence, Mass. 01843. This resulted in 14fractions with the following molecular weights:

TABLE V Amount M_(n) M_(w) Fraction (g) (1000 g/mol) (1000 g/mol)M_(w)M_(n) EXP10-1 18.50 18.8 88.8 4.72 EXP10-2 24.62 31.5 87.9 2.79EXP10-3 15.76 23.6 85.0 3.60 EXP10-4 10.24 17.0 80.9 4.76 EXP10-5 6.3614.6 44.1 3.01 EXP10-6 6.51 30.1 62.7 2.08 EXP10-7 5.93 37.3 72.9 1.96EXP10-8 6.65 48.0 91.9 1.91 EXP10-9 2.12 63.7 110. 1.73 EXP10-10 3.3078.9 128. 1.63 EXP10-11 3.38 88.1 138. 1.56 EXP10-12 1.83 88.0 146. 1.65EXP10-13 1.98 131. 220. 1.68 EXP10-14 1.96 145. 268. 1.85

Comparison of Commercial Polymers with Fractionated Polymer Samples

TABLE VI η₀ T η₀ Linear Equiv. G_(N) ⁰ η_(ext) Polymer (° C.) (Pa − s)(Pa − s) η₀/η*₁₀₀ (Pa) ratio A--LD-702 190 81740 71 2.3 × 10⁶ B--LD-113190 10000 19 2.3 × 10⁶ C--ECD-399L60 190 10500 3.3 2.3 × 10⁶ D--PL-1840190 20570 12.7 2.3 × 10⁶ E--ELVAX 3135 190 45000 45 2.3 × 10⁶ 4.12EXP10 - Bulk 190  6800 6.7 × 10³ 3.6 2.8 EXP10-9 190 12000 4.9 × 10³ 51.45 × 10⁶  1.43 EXP10-10 190 30000 8.1 × 10³ 9.1 1.7 × 10⁶ 2.5 EXP10-11190  >4.1 × 10⁴ 1.0 × 10⁴ >9.5 1.9 × 10⁶ 2.22 EXP10-12 190 >8.94 × 10⁴1.3 × 10⁴ >21 1.74 × 10⁶  3.15 EXP10-13 190 >1.95 × 10⁵ 5.0 × 10⁴ >331.45 × 10⁶  EXP10-14 190 >1.45 × 10⁶ 9.7 × 10⁴ >181 1.3 × 10⁶ note: Thevalues of the plateau modulus G_(N) ⁰ were calculated according to theequation G_(N) ⁰ = 4.83 G″ (ω)_(max), where G″ (ω)_(max) stands for thevalue of G″ at the frequency at which G″ is maximum, see R. S. Marvinand H. Oser, J. Res. Nat. Bur. Std., 66B, 171 (1962); and H. Oser and R.S. Marvin, ibid., 67B, 87 (1963). For comparison, the η₀ for a linearequivalent (same M_(w)) polymer is shown in col. 2 using the equation η₀(190° C.) = 5.62 × 10⁻¹⁴ M_(w) ^(3.36) (Pa − s) derived from Eq. 16,Mendelson, et al, J. Poly. Sci., Part A, 8, 105-126. (1970).

Discussion

Therefore we expect that the multiply branched comb and H-shapedpolymers of the invention and comb/linear copolymer blends are expectedto exhibit high levels of melt strength at low MIR in view of theirstrain thickening in uniaxial extension. The comb copolymers and theirblends with linear copolymers show strain hardening (even at low levelsof incorporation). Low levels of comb copolymers in a blends with linearpolymer will exhibit little effect on shear thinning (or MIR), but cancause a significant enhancement in strain thickening and melt strength.This gives one the opportunity to design for that combination ofproperties for those applications where it is desirable. The neat combsamples also exhibit the suppression of plateau modulus, asdistinguished from linear copolymers alone, and should be beneficial forextrudability.

We claim:
 1. A polymer consisting essentially of saturated hydrocarbonshaving: (a) a backbone chain; (b) a plurality of essentially hydrocarbonsidechains connected to (a), said sidechains each having anumber-average molecular weight of from 2,500 Daltons to 125,000 Daltonsand a MWD by SEC of 1.0-3.5; and, (c) and a mass ratio of sidechainsmolecular mass to backbone molecular mass of from 0.01:1 to 100:1,wherein said hydrocarbon polymers have (d) an M_(n) from 5,000 to1,000,000 Daltons, (e) an MWD by SEC of from 1 to 2.0, (f) a Newtonianlimiting viscosity (η₀) at 190° C. of said saturated hydrocarbon polymerat least 50% greater than that of a linear olefinic polymer of the samechemical composition and weight-average molecular weight, (g) a ratio ofthe rubbery plateau modulus at 190° C. to that of a linear polymer ofthe same chemical composition less than 0.83, and (h) a ratio of theNewtonian limiting viscosity (η₀) to the absolute value of the complexviscosity in oscillatory shear (η*) at 100 rad/sec at 190° C. of atleast
 5. 2. The hydrocarbon polymer composition of claim 1 wherein saidmass ratio is 0.1:1 to 10:1.
 3. The hydrocarbon polymer composition ofclaim 1 wherein said mass ratio is 0.3:1 to 3:1.
 4. The hydrocarbonpolymer composition of claim 1 wherein said mass ratio is 0.5:1 to 2:1.5. The hydrocarbon polymer composition of claim 1 wherein said backbonechain and said sidechains are derived from one or more of ethylene,propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene,1-dodecene, 4-methyl-pentene-1, styrene, alkyl styrenes, norbornene, andalky-substituted norbornenes.
 6. The hydrocarbon polymer composition ofclaim 1 wherein said backbone chain and said sidechains are essentiallyof an ethylene-butene copolymer structure.
 7. The hydrocarbon polymercomposition of claim 1 wherein said backbone chain and said sidechainsare essentially of an ethylene-propylene copolymer structure.
 8. Thehydrocarbon polymer composition of claim 1 wherein said backbone chainand said sidechains are essentially of an ethylene-hexene copolymerstructure.
 9. The hydrocarbon polymer composition of claim 1 whereinsaid backbone chain and said sidechains are essentially of anethylene-octene copolymer structure.
 10. The polymers of claim 1 whereinelement (g) is less than 0.3.
 11. The composition of claim 1additionally having (i) a ratio of the extensional viscosity measured ata strain rate of 1 sec⁻¹, 190° C., and time=3 sec (i.e., a strain of 3)to that predicted by linear viscoelasticity at the same temperature andtime of 2 or greater.